I would suggest that you finish both your pack and tarp as you may find that they end up a little heavier than you have planned for.

I just finished a Poncho/Tarp out of the Cuben material (48″ by 90″). With some reinforcement at the tie points and making a draw cord collar (Poncho mode) the total weight came up to 2.81oz. I have to be happy with the weight.

I will post some pictures when I get a chance to pitch it in the Tarp mode.

The backpack that I’am making is probably only around 1000 cu in or so made out of the Cuben Fiber CT0.6K.08 fabric so it is unbelievably lightweight. I think that it will weigh somewhere between 1.5-2 oz when finished. Pictures of your tarp would help me get ideas on how to make my ultralight tarp, also made from the CT0.6K.08 fabric.

I would agree that the backpack might be even less than what you think. The Pack I made used a .35oz version of the Cuben material. The pack without the mesh pockets weighed in under 1oz. This was a pack size of 6.5″ x 12″ x 33.5″ (2613 cu inches plus mesh pockets) counting the 10″ collar. The current Cuben material I have doesn’t seem to be consistent in weight and seems to run from .40oz to .50 oz per sq yard. I hope I am wrong in that thought. I am going to cut a piece 36″ by 36″ and weigh that and see what I get.

I am about ready to shift my gears back to my SUL AT Thru-Hike gear set. Because of the long duration of that hike anything under 5 pounds will be a good starting point. My guess is an under 3 pound set by the time I get finished with it.

Note that the mfg listed weight of the cuben fiber is in sailmakers yards,sm/yds, 28.5 X 36″.

The .35 is sm/yds and X 1.26 gets you the sq/yds.

I am also testing the material here at Mountain Laurel Designs. I’ll post my findings after I run the “Psycho Eternity Wind Seam Test.”

I have found the three lightest samples, down to about .2 oz sq/yds all very water proof but unsuitable due to stitching and seam hole creep under any stress, i.e. wind flapping.

It’s looking like the he .35 sm/yd mentioned is the lightest that may work UL gear.

The high cost, unproven long term use in UL gear, stitching and glueing reinforcements and the “unusual” stringy wax paper look will be factors in it’s use over proven standard .97 (or so) weight silicone spin fabrics now widely avialbe from various cottage tarp builders.

I have long understood what a sail makers yard is. I had a small sailboat for many years and even made a few of my own sails. They weren’t great but worked and I really surprised some friends that had boats like mine one day when I put up a Spinnaker that I had made. It worked but almost to well.

When I get a sample of fabric such as the 4 that I got from Cuben I calculate the square inches then weigh the sample on my Ohaus Triple Beam Scale. Then I can determine the weight of a 36″ by 36″ square yard. This is the only way I do it.

The lightest sample I got from Cuben was .29oz per sq yard. This is my calculation not Cubens. I got a 5′ by 4′ piece and made my first Pack Bag out of it. It seems that the lightest they have to sell at this time is the .40oz per stuff. I have 9 yards of that.

The fact that you found the material “unsuitable due to stitching and seam hole creap under any stress, ie. wind flapping” I found amusing.

This is where the science of engineering or cleverness comes into play. Just because you can’t figure out how to make something work doesn’t mean someone else can’t.

In my pre-prototype research I consulated a sail maker who uses the Cuben material. I have followed his suggestions since sails for really big boats are made out of this stuff all the time. What ever I make out of my Cuben fabric I don’t think it will ever be stressed like a sail underway in a strong wind. My construction strategy is sure to be different than yours and mine considers the whole of the item in the planning.

The high cost of this material NO, If you are making your own gear the cost of the material vs buying the item is not really a factor. My G6 pack cost X dollars and the pack I made simular to it cost much less in material alone. My labor is not a factor as I am doing this only for myself. I have a lot of the “proven standard” .96 – .97oz stuff and may never use it again.

Sorry, I did not mean to imply you might not understand any aspect of the fabric or weight measure systems and I agree with all of your good points.

I get a lot of questions about the spin weights and so I just wanted to give folks a very brief overview in case they are looking at the manufacturers sites and specs and are not familiar with the differences.

The Cuben fiber possibilities seem fairly new in the UL backpacker community and I look forward to super creative and inventive folks like yourself pushing the limits in DIY UL gear. Individuals who envision and create those developments like yourself have historically been the corner stone of future commercial and cottage industry offerings.

Sorry for any confusion or controversy in the thread. I guess that’s always a tough one in this medium when a manufacturer offers info or opinions in an open forum.

Hmm. I was just thinking: Perhaps you could ditch the mummy liner and the ground cloth–then replace it with a soft-top bivy, like an Equinox or BMW model. It won’t have the same ‘snuggle value’ as the silk, but would offer a little more insurance with the small tarp for about the same net weight.

How good are your normal material sewing skills? My suggestion is to buy a yard or two and practice with it. You will need to try sewing it using different stitch length and widths and see what set-up works best with your sewing machine. The needle and thread is also important and you should also find that out with practice.

There is a 2-sided tape that will work on this but I haven’t used enough of it to say how good or not good it is. The learning curve on the tape was slow for me. I did find out that sewing through the tape can be a sticky mess and require changing/cleaning my needle a lot..

Everytime I am asked about Cuben fabric I say this stuff isn’t for everyone.

I’m laughing at this aswell. You guys are amazing, but I fear your sense of proportion is getting lost somewhere.

If my base weight was under 5 lb, I would hardly notice it. If it was 1 lb or 2 lb I would drop it in my pocket and be off, to savour the sunset and skip happily across the americas. I might tie up my ‘pack’ in a bundle and hang it off a stick over my shoulder, just for the fun of it. I might add a few things to make life on the road simpler and easier. But I wouldn’t be figuring out where to shave off another 0.0005 of a gram…

Just joking, but you know what I mean, right? Keep it up, you guys. Awesome!

I wouldn’t have put it so bluntly as that, anon. If it wasn’t for these guys breaking new boundaries, we wouldn’t be able to follow in their footsteps. A pissing contest has no value; but this contest does have value.

I do wonder if there are other question which could be addressed now. Such as – this all sounds very theoretical; having got the weights this low, what would you really take, and why. You can easily allow yourselves some leeway here, eg. a tarp twice the size to keep the wind off, or a bag with a zip, or whatever. You could take the weight back up to 2 or 3 lbs total, and have double the enjoyment. Maybe this is the direction this list should be taking now?